The present invention relates to a storage system for storing data to be used by a computer in a computer system and, more particularly, to a storage system to be file-accessed through a network.
In recent years, the quantity of data to be handled in the computer increases so drastically that the capacity of the storage system for storing the data grows accordingly more and more. As a method for realizing the large-sized storage of a large scale but a lower cost, there is a storage system, which has a cluster configuration, an disclosed in U.S. Pat. No. 6,256,740.
The storage system of the cluster configuration is configured to have a plurality of storages (hereinafter referred to as “storage nodes”) of a relatively small configuration are coupled to each other through switches or the like. In this configuration, the cluster configuration storage system can be configured by coupling a plurality of storage nodes according to the storage capacity needed, so that storage systems having various capacities from small to large ones can be scalably realized.
As one kind of the storage system, on the other hand, there is a Network Attached Storage (hereinafter referred to as “NAS”). This is a storage system capable of accepting a file access through the network, and in fact, it is configured by a computer (hereinafter referred to as “NAS server”) for providing the file system and a storage such as a disk device. Here, the “file” indicates a cluster of the data to be recognized by the user in the file system or the like.
The NAS is a storage system, which is usable because the user can use the file access directly. However, a protocol (e.g., the NFS) for accessing the NAS is premised by the use of the TCP/IP (Transmission Control Protocol/Internet Protocol). As the frequency of the access to the NAS rises, therefore, the processing load on the TCP/IP in the NAS raises a problem. As a technique for solving this problem, there is disclosed in PCT International Laid-open No. 02/069166 a technique, in which the processing of the TCP/IP is separated from the NAS server into a single hardware (hereinafter referred to as “TCP/IP processor”) and in which the TCP/IP processor and the NAS server are accessed through a switch. In PCT International Laid-Open No. 02/069166, the command issued by the computer is processed up to the TCP/IP layer by the TCP/IP processor and is then processed by the NAS server. In case the NAS server accesses the storage, there is used the storage which is connected to the SAN through Fiber Channel Switching Module.